For example, the technique examined by the inventors of the present invention in the field of a serial communication device such as the car navigation system is shown below.
More specifically, in the communication device in which the serial data is received and decided at the read timing of the predetermined number of times, the cycle of the communication process which determines this read timing is measured, and this read timing is hastened in order to prevent the case where the data cannot be decided when the read timing is delayed by the other interrupt process in the communication device (e.g., Japanese Patent Laid-Open No. 8-314513).